This application claims the benefit of German patent application DE P 10052672.1, filed Oct. 24, 2000, herein incorporated by reference.
The present invention relates to a rotary drive for use in conjunction with an arrangement for cleaning a spinning rotor having a tool for introduction into the rotor for cleaning contact with an interior rotor surface to be cleaned.
Open-end rotor spinning machines are used almost exclusively to process cotton fibers or fiber blends containing cotton fibers as their main component. However, natural fibrous materials contain impurities that in some instances can have a significant adhesive character, such as, e.g., pectin, wax, and the like which occur naturally in the cotton fibers. These impurities tend to become deposited in the rotor groove. As a result, the rotor groove becomes increasingly clogged over time, which distinctly reduces the spinning stability and the quality of the yam produced. For this reason, these impurities are usually removed from the rotor upon a yarn break before spinning is restarted. Moreover, it is possible to perform a preventive cleaning, which is especially necessary if yarn breaks or other interruptions seldom occur. In this instance, the spinning process is purposely interrupted in order to perform this cleaning.
Many variants of this cleaning process, as well as the devices used for the cleaning process, constitute the subject matter of a great number of patent applications.
German Patent Publication DE 26 29 161 C2 describes a maintenance device for the spinning units of an open-end rotor spinning machine in which various cleaning tools, such as scrapers, brushes or blowing nozzles, are used. These cleaning tools are attached to a rotatable shaft that is moved along the rotor shaft for the cleaning process until the cleaning tools have passed the rotor opening and reached the plane of the rotor groove. However, since the rotor opening has a smaller diameter than the rotor groove (which is at the location of the greatest rotor diameter), the cleaning tools may not have sufficient radial extension from the rotor shaft required to reach the groove after passing the rotor opening. This situation was improved by fastening the cleaning tools to spring elements that are bent outward during the rotation of the shaft carrying the cleaning tools by the centrifugal forces occurring thereby until the cleaning tools make contact with the rotor groove.
This improvement however has the particular disadvantage that the cleaning tools are deflected radially and tangentially when they meet impurities until they are free of the impurity. The tools thereby start to oscillate, which prevents their proper contact with the rotor groove, which contact should be as long as possible for a complete cleaning. In addition, the force directed in this manner against the impurities is limited and thus does not lead to the desired cleaning result. First and foremost, however, rotating cleaning elements tend to accumulate fiber windings. This problem causes the tools to become constricted to the point that the tools may no longer be able to extend outwardly in the required manner at the next cleaning process.
German Patent Publication DE 35 30 879 A1 teaches a method and a device for rotor cleaning that makes use of a rotatable blower device corresponding with a suction bell also present otherwise in German Patent Publication DE 26 29 161 C2. Only impurities which are fairly easily detachable can be eliminated by the exclusive use of compressed air. On the other hand, stubborn impurities can only be detached from the surface of the rotor groove by a mechanical method.
In order to counter these disadvantages, German Patent Publication DE 37 15 934 A1 teaches a cleaning device in which the rotor itself is caused to rotate by a drive roller that can be placed laterally on the outer side of the rotor whereas a mechanical cleaning tool in the form of a scraper is shifted obliquely through the rotor opening into the rotor groove and then held in contact with the rotor groove. Even stubborn impurities can be readily eliminated by such a scraper.
The above device has the disadvantage, however, that radial forces are exerted on the rotor during the drive that can result in a varying deflection of the rotor as a function of the design of the radial support. This problem is especially critical if the rotor is supported in a non-contact manner, e.g., by magnetic and/or gaseous support. In addition, the maintenance unit and the rotor are not always aligned totally identically to one another. In this instance, a reinforcement of this deviation can result on account of the radial forces. This problem can also have the result, among other things, that the contact of the cleaning tool with the rotor groove is not intensive enough or at least not uniform enough to perform an unobjectionable rotor cleaning.
The present invention therefore has the object of further improving the above-described state of the art and, in particular, to provide for improved rotor cleaning.
The invention addresses this object by an improved rotary drive for use in conjunction with an arrangement for cleaning a spinning rotor having a tool for introduction into the rotor for cleaning contact with an interior rotor surface to be cleaned. According to the present invention, the rotary drive comprises an entraining device for contact with an exterior rotor surface for imparting rotary movement to the spinning rotor during cleaning, the entraining device being arranged relative to the spinning rotor to mutually cancel radial forces generated by the rotary drive and the spinning rotor by the contact therebetween when the rotary drive and the spinning rotor respectively rotate about a common axis of rotation.
Due to the arrangement of the entraining device in accordance with the present invention, the spinning rotor is not exposed to any radial force while being driven by the rotary drive for rotor cleaning if the axes of the rotary drive and of the spinning rotor are in alignment. Possible slight errors of adjustment are in a range of 1 mm and do not result in the generation of disturbing radial forces. Such minor misalignment can be compensated, e.g., by an appropriate degree of play in the suspension of the rotary drive or by an elasticity of the mounting of the entraining device or of the entraining device itself. Optionally, a mutual centering between the rotary drive and the spinning rotor can also take place during the driving of the rotor.
The entraining device preferably comprises one or more entraining elements, e.g., a closed ring or several entraining elements arranged on a circular support. The decisive factor is that the ring or the circular support is arranged at a right angle to the axis of the rotor shaft in order to assure the required centering. In any case, the arrangement should be selected so that no resulting radial forces remain.
The entraining elements are advantageously attached directly on the electric rotor of the rotary drive, that is preferably designed as an outside rotor motor.
In order to assure an effective driving engagement of the spinning rotor, the entraining elements preferably have an anti-slip gripping surface at least on the portion thereof which contacts the spinning rotor. Entraining elements comprised of an elastic material are especially suitable in order to also assure that cleaning tools arranged on the same advancing element can be exactly positioned so that they meet the rotor groove.
If the entraining elements comprise, e.g., rubber magnets, no pressure or force need be exerted via the advance of the rotor drive unit because the entraining elements are thereby coupled by magnetic force to the ferromagnetic spinning rotor.
In order to be able to bring the entraining elements and the cleaning tools in contact with the rotor, a positioning device is utilized to shift the entire cleaning device axially to the spinning rotor. This positioning device preferably has a control device that makes possible an exact positioning relative to the spinning rotor.
However, it is alternatively contemplated under the present invention that the cleaning tool can shift axially relative to the rotary drive so that the contacting of the entraining elements with the rotor and the immersion depth of the cleaning tool into the rotor opening can be separately controlled.
According to a further feature of the invention, the spinning rotor is freed from an axial force component during its drive for cleaning the rotor since an axial contract pressure is not necessary when the spinning rotor is engaged between the entraining elements.
The invention is explained in further detail in the following description with reference to exemplary embodiments illustrated in the accompanying drawings.